As John Reed points out , the phrase “Eagle” is abused, inconsistent, and overused. And even though Earle Neale’s “Eagle” defense is celebrated, it’s hard to know exactly what it is. Jene Bramel’s excellent series on pro defenses shows something akin to a 5-2-4 Oklahoma (father of the modern 34), but the diagram of Neale’s Eagle defense in Ryan and Walker’s 46 book (page 10) looks something more like this:

According to Ryan and Walker, Earle Neale's Eagle looked something like this.

This latter diagram is more believable, since people do claim that dropping the nose guard in Earle’s defense led to a kind of 4-3 (Or in Steve Belichick’s notation of the time, a 45 – back in the 1950s, corners would be sometimes be counted as linebacker depth players).

The three players in the middle – the diamond – are a 0 technique nose tackle, and two 3 technique tackles. The 3 technique tackles can also be called eagles – terminology used in odd front 4-3s and also certain derivatives of the 46. These sons of the 46 are often called double eagle defenses because of the 46 “diamond“, which they inherit from Buddy Ryan’s defense.

The most important of these defenses is called the Desert Swarm defense, made famous by Dick Tomey during his period as Arizona’s head coach. This defense lives on in college through the work of Rich Ellerson, currently the head coach at Army, who was a defensive staffer during Tomey’s run at Arizona. Though a number of sources call this defense a 4-3, it’s more an 8 in the box defense of the Ryan family, with the strong safety playing more of a linebacker technique, and the alignment to me looking quite a bit like a 5-3. To note, in the Desert Swarm, one of the 3 techniques (usually the weak side tackle) is a flexed tackle. Ironically, in the photo below, the flex tackle is on the strong side of the formation.

Literature on this defense is a little hard to come by. Some links that you might find useful are given below.

To summarize: a double eagle defense is one with a nose guard and 2 3 technique tackles. A double eagle flex has one flexed tackle. A double eagle double flex has two flexed tackles. Earle Neale’s Eagle appears to be a double eagle, though no one is 100% certain. These defenses should not be confused with the 34 Eagle of Fritz Schurmer, which is an eagle of an entirely different color.

Update: a more nuanced look at Fritz Schurmer’s Eagle can be found here.